1. Field of the Invention
The present invention relates generally to a handle operated, heavy duty, toggle type draw latch for connecting two relatively movable members, and for exerting force that tends to draw the two members relatively toward each other, with the latch having components that cooperate to provide an unusually rugged unit. More particularly, the present invention relates to a handle operated toggle latch featuring ruggedly constructed components that cooperatively interact when the latch is "latched" to reinforce each other to enhance the capability of the latch to withstand heavy direct draw force and forces that tend to cause latch components to twist, rack and bend. The latch features a base of novel configuration, and a relatively complexly configured handle that cooperates with the base and with other latch components of provide stops for limiting the ranges of movement that can be executed by relatively movable components, and preferably also includes a lockable safety catch for securely retaining the handle in a closed position until the safety catch is operated to release the handle for movement to an open position.
2. Prior Art
Toggle latches of a variety of types have been proposed for use in releasably joining two relatively movable members. Usually, what is referred to as a "toggle latch" has at least a pair of pivotally interconnected, link-like components that are "toggled" through an "over center" position to effect latching and unlatching movements.
Toggle latches that are operable to releasably join and to draw two relatively movable members toward each other are sometimes referred to as "draw latches." Usually, a toggle-type draw latch includes a latch assembly that can be mounted on a first of two relatively movable members, and has what is referred to as a "drawbar" that can be moved, when the latch is "open," into and out of connection with a latch-engageable formation that is connected to the second of the relatively movable members. When components of the latch are moved latchingly toward a "closed" position, the drawbar serves not only to engage the latch-engageable formation to join the first and second relatively movable members but also to exert force on the latch-engageable formation that tends to move the members relatively toward each other.
While some toggle-type draw latches rely solely on tension force that is applied through over-center connected components to retain latch components in their "closed" positions, proposals have been made to use spring acting safety catches of various forms to releasably retain latch components closed. Some proposed safety catches are mere leaf springs, portions of which are deflectable for movement into and out of latching engagement with relatively movable components--an arrangement that may not be well suited for use in a high-load application where vibration is present. Another safety catch proposal calls for the use of a spring-biased slide carried on one movable component for being received in an aperture defined by another movable component--an arrangement that involves no secure connection of the safety catch to a stationary base member, and that is not lockable to secure the safety catch.
Most prior toggle latch proposals are intended to address relatively light duty applications--applications that require toggle latches to regularly withstand less than a thousand pounds of direct draw force. Previously proposed handle operated, toggle type draw latches have not exhibited a desired degree of ruggedness to withstand use in high load applications, for example in securely retaining large, heavily loaded, interstate and international cargo containers in place during over-the-road transport atop the flat beds of highway vehicles such as semi-trailer trucks. Such applications often require that the latches used to hold cargo containers in place be capable of withstanding not only tons of direct draw force but also correspondingly high transverse force loadings that tend to twist, rack and bend latch components.
3. The Referenced Parent Applications
The two co-pending utility applications that are referenced above disclose handle operated toggle latches that are designed to withstand lighter loads than are capable of being addressed by latches that embody features of the present invention. However, some latch features that are disclosed in the referenced applications are incorporated in latches that embody the preferred practice of the present invention. One such feature is a base-mounted safety catch that engages a handle-carried formation for releasably retaining a latch operating handle in its closed position, and that can be "locked" using a conventional padlock to add a degree of security.
Another feature disclosed in the referenced co-pending utility applications is the use of two elongate, complexly configured stamped metal members (that essentially are left and right "mirror images" of each other) that are rigidly connected to extend in side by side relationship to form an operating handle that is pivotally connected to a base and to a drawbar of a toggle latch. This concept, suitably modified to provide a considerably more rugged handle assembly, finds use in latches that embody the preferred practice of the present invention.